Temperature is one of the main factors in determining the output power obtainable from a laser. Therefore, management of the heat generated during laser operation is critical to overall performance, and one aspect of the problem of maintaining a controlled thermal environment is to provide a cooling system which efficiently and effectively dissipates the heat.
Heat dissipation can be accomplished by several methods, principally by liquid cooling or air cooling. Liquid cooling directly pumps liquid through either the cavity or electrodes and removes the heat generated in the lasing media. Air cooling also removes the heat generated in the lasing media and dissipates it outside the laser cavity by forcing air over external heat sinks. Each method has its advantages and disadvantages.
The overall size of a forced air cooled laser has tended to be significantly larger than that of a liquid cooled laser due to the need for heat sinks with large surface areas, fans and their mounting provisions and enclosures to direct the air across the heat sinks. Examples of such prior art air cooled laser structures may be found in U.S. Pat. Nos. 5,901,167, 5,550,853 and 5,253,261. This size constraint has put conventional air cooled lasers at a disadvantage when space constraints are an issue.
A primary disadvantage of conventional air cooled lasers as compared with liquid cooled lasers is that liquid cooled lasers have had the ability to operate over a wider temperature range without significant degradation in performance.
However, while liquid cooling is efficient, it has several disadvantages as well. One problem is that condensation can occur in humid environments when the liquid temperature is not managed carefully enough or when the ambient temperature changes. Condensation can damage the optics and electronics.
Another problem is that the chillers/heat exchangers for cooling the liquid are expensive, bulky and prone to require maintenance. Additionally, leaks of the cooling liquid can damage the laser as well as other equipment in the vicinity of the leak.
Conventional air cooled lasers such as disclosed in the three cited patents have traditionally employed AC/DC cooling fans with low pressure capability (0-5 inches of water). Fans with limited pressure capability force the use of heat sinks with a low surface area to volume ratio. This results in a structure having a few tall fins with large gaps in between. The limited pressure capability of these fans also requires their close proximity to the heat sinks, further enlarging the laser package. Therefore liquid cooling (typically using water) has tended to be the non-exotic cooling method of choice for cooling a laser when small size and a wide temperature range are required.
Accordingly, there remains a need for a structure and method that enables an air cooled laser to achieve efficient heat dissipation in combination with minimal size and the ability to operate over a wider temperature range without the disadvantages of water cooling.